If you marry into a family how does your husband get joint custody?
Your husband cannot get joint custody of your children from a prior marriage. Custody arrangements are made between parents of children. Your present husband can legally adopt your children with their father's consent. He would then have all the legal rights and obligations of a biological father. The children would become his legal heirs-at-law.
If you marry and take joint custody of children of your wife will you be required to pay child support in the case of a later divorce?
Firstly, she has to obtain talak (divorce) from her first husband, after which the question of remarriage arises. The pertinent question that may arise is that under whose custody the baby will stay. If the first husband refuses to take care of the baby, will the second husband be agreeable to marry the woman with her baby ?